111ec0179_vishal mishra_design of ask fsk psk receivers (2)
DESCRIPTION
1TRANSCRIPT
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DESIGN OF ASK FSK PSK RECEIVERS USING ORCAD AND
MULTISIM
SUBMITTED BY: VISHAL MISHRA
111EC0179
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AIM:
To design receivers for ASK, FSK and PSK modulated signals.
SOFTWARE USED:
ORCAD 16.6 CAPTURE CIS LITE and NI MULTISIM
THEORY:
Ask Receiver:-
The circuit used here is the asynchronous ASK detector. When the signal passes
through a rectifier we get positive half wave signal. By using low pass filter we can
detect the envelope of the signal.in the circuit first op-amp acts as the amplifier in
inverting configuration to amplify the incoming signal. Diode acts as the rectifier
which converts the signal to a half wave signal. Resistor and the capacitor
combinely forms the low pass filter and acts as envelop detector. Second op-amp
with the combination of pot, resistor, diode, and capacitor forms a comparator.
The entire process can be represented with a simple block diagram.
FSK receiver:
In this SPICE simulation two pass band active filters resonant at the frequencies
corresponding to the mark and space states are used in place of the phase lock loop
(PLL) for data recovery. The input signal is an FSK signal read from a file. This signal
is then applied to two band pass filters tuned to 2 kHz and 4 kHz. The output from
each filter is then rectified. Two low-pass filters, with pass band and stop band edge
frequencies of 100 Hz and 2 kHz, to filter the doubled frequency after squaring, are
then connected to a comparator to recover the original data.
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PSK Receiver:
This PSK demodulator contains balanced modulators for recovering data from the
PSK signal by multiplying the band pass PSK signal by an identical carrier. The local
oscillator can have errors in frequency and phase placed to simulate the non-
coherent conditions. The recovered data output signal from the centre-tapped
transformer uses a low-pass filter to remove unwanted high-frequency
components.
CIRCUITS AND OUTPUTS:
ASK RECEIVER:
ASK RECEIVER CIRCUIT
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ASK GENERATED SIGNAL
RECOVERED SIGNAL
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FSK RECEIVER:
FSK CIRCUIT
FSK GENERATED
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FSK FILTER OUTPUT
FSK RECOVERED
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PSK RECEIVER:
UPPER HALF OF CIRCUIT
LOWER HALF OF CIRCUIT
PSK CIRCUIT
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PSK GENERATED SIGNAL
PSK RECEIVER SIGNAL
CONCLUSION:
The circuits were implemented using the softwares and outputs were as shown. ASK
was implemented in multisim software while PSK and FSK were implemented in
ORCAD.